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I ran into the issue where no reloading manual had the data for the bullet weight and powder that I wanted to use in my reloads so I thought that I'd post how I figured out the loads to start my load development.
I'm working on developing some loads for a Ruger No.1 chambered in 7X57 (7mm Mauser) and I'm playing with the 150 grain Nosler Partition bullets (for out of California hunting).
Looking through the powder cabinet I had 3 good choices for the 7X57 with heavier bullets, Reloder 15, H4831 and H4350. H4831 had the best velocity but I was getting low in the can and I need some for my 7mm Magnum.
So, just to be different I decided on using the Alliant Reloder 15. But, unfortunately Reloder 15 does not have any formulas for 150 grain bullets, much less the 150 grain Partition. (The Nosler, Lee, Hodgon and Hornady manuals also do not have data for Alliant Reloder 15 and 150 grain bullets)
Alliant's data for the 7mm Mauser using Reloder 15 powder
Bullet ........................Case ...............OAL ......Primer .....Chg ......Velocity
Speer 145 gr SP ..........Remington.......2.8 ........CCI 200 ... 42 ...... 2,598
Speer 175 gr SP ..........Remington ......3.015......CCI 200 ...38 ...... 2,282
So, as you can see the recipes are very specific and all Alliant provides is a maximum load with no pressure numbers. So what I did was extrapolate the data provided to figure a maximum charge for a 150 grain bullet;
With 145 grain bullets the max charge is 42 grains and with a 175 grain bullets it is 38 grains so there are 4 grains of powder weight difference for 30 grains of bullet weight difference.
Dividing the difference in powder weight (4) by the difference in bullet weight (30), that means that for every grain increase in bullet weight you have to reduce the powder charge weight by (4/30) .133333 grains.
So for a 150 grain bullet, I figured that the maximum charge would be: the max charge for a 145 grain bullet (42 grains) – (5 times .1333333), 5 grains which is the difference between the 150 grain Partition and the 145 grain Speer,
That equals 42 – (5 x.13333) or 42 - .6666666 = 41.33333 grains
Since the rest of my components don’t match the Alliant recipe the prudent thing to do is reduce that limit by 10% and use that as a starting load. So, my starting load will be 37 grains of Reloder 15 and I’ll work up in 0.5 grain increments until I feel comfortable with the pressure signs and velocity.
There is more actually more safety margin than the 10% implies since Alliant’s max pressures are based on the SAAMI max pressure for the 7x57 cartridge at 51,000 PIS (46,000 CUP) because of all the older rifles chambered in the cartridge.
CIP (Intl regulating agency) says that the 7 Mauser brass must be specc’ed to withstand 56,565 PSI and I’ll be shooting these loads out of my Ruger No. 1 rifle which is chambered in cartridges up to 62,000 PSI so there is a lot more safety margin than I need.
Anyway, that's just one way of calculating starting loads when you don't have the exact formula in any of your manuals.
I'm working on developing some loads for a Ruger No.1 chambered in 7X57 (7mm Mauser) and I'm playing with the 150 grain Nosler Partition bullets (for out of California hunting).
Looking through the powder cabinet I had 3 good choices for the 7X57 with heavier bullets, Reloder 15, H4831 and H4350. H4831 had the best velocity but I was getting low in the can and I need some for my 7mm Magnum.
So, just to be different I decided on using the Alliant Reloder 15. But, unfortunately Reloder 15 does not have any formulas for 150 grain bullets, much less the 150 grain Partition. (The Nosler, Lee, Hodgon and Hornady manuals also do not have data for Alliant Reloder 15 and 150 grain bullets)
Alliant's data for the 7mm Mauser using Reloder 15 powder
Bullet ........................Case ...............OAL ......Primer .....Chg ......Velocity
Speer 145 gr SP ..........Remington.......2.8 ........CCI 200 ... 42 ...... 2,598
Speer 175 gr SP ..........Remington ......3.015......CCI 200 ...38 ...... 2,282
So, as you can see the recipes are very specific and all Alliant provides is a maximum load with no pressure numbers. So what I did was extrapolate the data provided to figure a maximum charge for a 150 grain bullet;
With 145 grain bullets the max charge is 42 grains and with a 175 grain bullets it is 38 grains so there are 4 grains of powder weight difference for 30 grains of bullet weight difference.
Dividing the difference in powder weight (4) by the difference in bullet weight (30), that means that for every grain increase in bullet weight you have to reduce the powder charge weight by (4/30) .133333 grains.
So for a 150 grain bullet, I figured that the maximum charge would be: the max charge for a 145 grain bullet (42 grains) – (5 times .1333333), 5 grains which is the difference between the 150 grain Partition and the 145 grain Speer,
That equals 42 – (5 x.13333) or 42 - .6666666 = 41.33333 grains
Since the rest of my components don’t match the Alliant recipe the prudent thing to do is reduce that limit by 10% and use that as a starting load. So, my starting load will be 37 grains of Reloder 15 and I’ll work up in 0.5 grain increments until I feel comfortable with the pressure signs and velocity.
There is more actually more safety margin than the 10% implies since Alliant’s max pressures are based on the SAAMI max pressure for the 7x57 cartridge at 51,000 PIS (46,000 CUP) because of all the older rifles chambered in the cartridge.
CIP (Intl regulating agency) says that the 7 Mauser brass must be specc’ed to withstand 56,565 PSI and I’ll be shooting these loads out of my Ruger No. 1 rifle which is chambered in cartridges up to 62,000 PSI so there is a lot more safety margin than I need.
Anyway, that's just one way of calculating starting loads when you don't have the exact formula in any of your manuals.
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